Full size or tiny toy, the technology is the same, but easier to fit to a large airframe.
OK, go ahead and find a manufacturer willing to build it for you!
I see everyone is neatly skirting around the security/terrorist issue but until world terrorism that could interfere is totally secured fully automated flight won't happen.
People on here who argue that pilotless aircraft will not happen because nobody will insure them/certify them have missed the point. As these systems improve, it may be that insurers will only insure pilotless planes.
I will take a large bet with you that the insurance industry will be the last to come on board and that initial rates will be sky high, if not prohibitive. You will need to convince underwriters that the risk they take now, of an airframe falling into the centre of a big city, is greater than that of computer only flown aircraft. Good luck with that! (spent three years in the London aviation insurance industry way, way back but the principles don't change).